This invention relates to a battery charging system for a marine propulsion unit and more particularly to an improved arrangement for charging a pair of batteries from an alternator.
In many applications a storage battery is employed for powering electrical devices and this storage battery is charged by an alternator driven by an internal combustion engine. A wide variety of vehicles including watercraft incorporates such systems. Frequently it is also the procedure to employ plural batteries that are wired in parallel so as to provide safety and insurance against a loss of power even in the event one battery becomes depleted. However, when both batteries are charged in parallel, it has been the practice to provide a battery isolator between the rectifying diode circuit and the batteries so as to protect the circuit and other battery in the event one of the batteries becomes defective. Such isolators are normally provided in a separate circuit between the rectifying diodes and the batteries as a separate connector or isolator that includes a plurality of diodes, one being connected to each of the batteries. Such arrangements, however, are unsatisfactory for a variety of reasons.
Specifically, the provision of the separate battery isolator further complicates the wiring and obviously adds to its cost. In addition, the fact that the diodes are added elements to the system give rise to a drop in voltage which lowers the charging performance of the system.
FIGS. 1 and 2 are views showing an outboard motor charging a pair of batteries and the electrical circuitry therefore, respectively, of a prior art construction. It will be noted that an outboard motor 11 has a combined magneto generator system including a flywheel 12 that includes a generating coil 13. The generating coil 13 supplies electrical power to a terminal 14 through a charging circuit, indicated generally by the reference numeral 15. This charging circuit 15 includes a voltage regulator 16 which is associated with a pair of diodes 17 on the opposite ends of the charging coil 13 and a rectifying circuit including pairs of diodes 19 and 21 that output a generally constant direct current voltage to the terminal 14.
A pair of batteries 22 have one of their terminals (in this case the positive terminal) in circuit with the terminal of 15 through a parallel circuit that includes an isolator 23. As may be seen, the isolator 23 includes a pair of diodes 24 that are in parallel circuit and which will protect one battery 22 in the event the other battery becomes defective. As afore described, the isolator 23 not only adds to the complexity and cost of the device but also the diodes 24 act to reduce the charging efficiency.
It is, therefore, a principal object to this invention to provide an improved arrangement for charging plural batteries from a magneto generator or alternator.
It is a further object of this invention to provide a charging circuit for charging a plurality of batteries wherein the use of a separate electrical isolator to protect the remaining battery or batteries in the event of a defective battery is unnecessary.